Since the invention of the fireplace and thermosiphonic chimney in accordance with the respective United States patents of Robert K. Thulman, mentioned above, it has been possible to construct fireplaces and chimneys in a factory for future installation in residential or other buildings. Use of such factory-built fireplaces and chimneys has permitted the saving of construction expenses by limiting or eliminating the masonry work and material that had previously been necessary in the construction of a fireplace and the chimney therefor. Inasmuch as the outer surface of factory-built fireplaces and chimneys can be maintained at a temperature only slightly above that of the surrounding air, it has become possible to mount them in direct contact with wood or other combustible material used in the structure of a building. Moreover, elimination of a masonry chimney has rendered unnecessary the massive and expensive footings which had previously been required in order to furnish adequate support to masonry fireplaces and chimneys.
Although the factory-built fireplaces and chimneys as just described have caused much progress in construction methods by virtue of savings of time, material, and money, they have not in themselves provided much improvement in the heating of the structure in which they are accommodated.
Efforts have been made in the past to increase the amount of heat supplied by a factory-built fireplace to its environs within the structure that accommodates it. An example of one type of improvement is the so-called "circulator fireplace" as manufactured and marketed by The Majestic Company, a Division of American Standard Inc. situated in Huntington, Indiana. Such circulator fireplaces have heavy, double-walled steel fireboxes and are designed to be framed in masonry and used with a conventional masonry chimney. Circulator fireplaces provide paths for inward convection of air through openings low in one or both of the outer side walls of the fireplace structure whereby the air flows in to be heated by contact with an intermediate or an inner wall of the fireplace structure. The air so heated is then allowed to rise and return outwardly through an opening in the upper part of the outer fireplace wall to warm the room in which the fireplace is located. Sometimes circulator fans have been provided in order that the flow of air to be warmed by contact with the inner fireplace wall should not be entirely dependent upon convection. In any event, circulator fireplaces of this type have functioned simply by transferring a small amount of heat from the fireplace to the air in the room. Such a practice has not been very effective in heating the room in which the fireplace is located, and has not provided a convenient way to heat other rooms of the structure. Moreover, room air circulated between the walls of the fireplace has furnished no cooling to the flue of the chimney, through which the combustion products of the fireplace are discharged.
Accordingly, it is an object of our invention to provide a fireplace system in which a substantial amount of heat generated by combustion in the fireplace is made available to a room of the structure in which the fireplace is located.
Another object of our invention is to furnish a system in which a substantial amount of heat developed by combustion of fuel in the fireplace (or a similar source of heat) can be made available to rooms other than the room in which the fireplace is located.
A further object of our invention is to provide cooling of the chimney flue which is more effective than the cooling accomplished by the respective inventions disclosed in the two aforementioned Thulman patents. Such augmented cooling of the flue is especially important when an extremely hot fire is present in the firebox of the fireplace, thereby generating effluent gases of very high temperatures.
Still another object of our invention is to provide a fireplace system in which the degree of cooling of the chimney flue increases with the need for such cooling. An objective is to furnish a large volume of cooling air to the flue at the very times when an especially hot fire in the fireplace maximizes the need for cooling of the flue.
A still further object of our invention is to furnish a controllable source of heat to the room in which the fireplace is located, and optionally also to other rooms of the same structure.